Projection television screen

ABSTRACT

A television screen is provided with one or more substrates made of a thin film. A number of materials may be used for the film substrate. Further, structures are formed on one or more resin bearing surfaces of the film substrates using a number of techniques, including using patterned rollers to press against the resin bearing film surfaces. The resin can be liquid resin that is cured to set the patterned structures. The thin film results in stronger yet lightweight televisions screens that are safe and easy to handle.

BACKGROUND OF INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a projection television receiverand, more particularly, to a viewing screen for a projection televisionreceiver.

[0003] 2. Description of the Related Art

[0004] The viewing screen of a projection television receiver(hereinafter “projection television screen”) is usually wider than theviewing screen of a conventional television receiver and thus weighsmuch more than the viewing screen of the conventional televisionreceiver. A projection screen should be mechanically strong but not tooheavy. Since a projection television screen is an exposed component ofthe television receiver, it is vulnerable to impact damage when thereceiver is handled, used or moved.

[0005] A conventional projection television screen is made from anextruded polymethylmetacrylate(PMMA) sheet, which may be either a plainsheet or a sheet with shapes formed upon it to facilitate its variousfunctions. PMMA sheets are heavy and have low mechanical strength andespecially low impact strength. When a conventional projection screen isbroken by an external impact, the pieces are very dangerous because theyhave many sharp edges.

SUMMARY OF THE INVENTION

[0006] An object of the present invention is to provide a projectiontelevision screen that it is safe, light, and mechanically strong.

[0007] Another object of the present invention is to provide acontinuous-mode process for making a projection television screen thatis safe, light, and mechanically strong.

[0008] In order to accomplish the above objects, the projectiontelevision screen of the present invention is made of a thin transparentfilm with high mechanical strength. Shapes may be formed on the surfaceof the film made of photo-curing resin in order to perform the necessaryfunctions. After that, another type of film could be attached onto theshape formed on the substrate. The resultant structure according to thepresent invention is used as a projection television screen.

[0009] Yet another object of the present invention is to provide amanufacturing process for providing a screen which is described above.While in prior an a screen has been manufactured in a non-continuous waybecause only a planar shaped die is available in the prior art, with themanufacturing process of the present invention, a roll-shaped die can beeasily fabricated using an electroforming method. Thus, continuousmanufacture of a screen can be accomplished.

BRIEF DESCRIPTION OF DRAWINGS

[0010] These and other advantages and features of the present inventioncan be better understood with reference to the following descriptionwhich will be described in conjunction with the accompanying drawings inwhich:

[0011]FIG. 1 illustrates the use of a projection television screen.

[0012]FIG. 2 illustrates the structure of a projection television screenaccording to an embodiment of the present invention.

[0013]FIG. 3 illustrates the detailed structure of the projectiontelevision screen shown in FIG. 2.

[0014]FIG. 4 illustrates a process of manufacturing a projectiontelevision screen according to an embodiment of the present invention.

[0015]FIG. 5 illustrates a conventional process of manufacturing anobjective lens.

[0016]FIG. 6 illustrates a conventional process of manufacturing aFresnel lens.

[0017]FIG. 7 illustrates a second conventional process of manufacturinga Fresnel lens.

[0018]FIG. 8 illustrates a process of fabricating an electroforming rollsuitable for manufacturing the Fresnel lens and the objective lens ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] As shown in FIGS. 2 and 3, a projection television screen 1 ofthe present invention comprises: a Fresnel lens 4; an objective lens 5adjacent to and optically aligned with the Fresnel lens 4; and atransparent protective sheet 6 adjacent to the surface of the objectivelens 5 furthest from the fresnel lens 4.

[0020] The Fresnel lens 4 comprises: a first transparent substrate 8;and a phase grating 7 mounted on the surface of the first substrate 8nearest the objective lens 5. The Fresnel lens 5 collimates light froman image protector 3 and uniformly projects the collimated light ontothe surface of the objective lens nearest the Fresnel lens 4. The phasegrating 7 is formed from a resin that is cured by exposure toultraviolet light (hereinafter “ultra-violet resin”) after the shape ofthe grating has been impressed upon the fluid resin.

[0021] The objective lens 5 comprises: a second transparent substrate10; a plurality of lenticular structures 9 mounted on both surfaces ofthe second substrate 10; and an anti-reflective layer 11 mounted on thesurface of the second substrate 10 furthest from the Fresnel lens 4. Theobjective lens 5 collects parallel red, green, and blue image beams fromthe Fresnel lens 4 at a predetermined position of each of the colorcell. The anti-reflective layer 11 absorbs stray ambient light and thusbrightens the images on the screen.

[0022] The ultra-violet resin used to make the grating 7 may also beemployed to make the lenticular structures 9. The type of film used forthe substrate 8 of the Fresnel lens may also be employed for thesubstrate 10 of the objective lens. A diffision agent may be used,depending on the degree of light diffusion required, the ultra-violetresin used to make the grating 7. An ultra-violet curing black ink withextinction and adhesion characteristics is employed, for theanti-reflective layer 11.

[0023] The protective sheet 6 protects the Fresnel and objective lensesagainst damage from outside. The material of the protective sheet 6 maybe the same as that of the substrate 8 of the Fresnel lens or thesubstrate 10 of the objective lens. If desired, various coatings such asan anti-reflection coating and a scratch-resistant coating may beapplied to the protective sheet 6. The protective sheet may also becolored.

[0024] The viscosity of the ultra-violet resin used to make the grating7 and the lenticular structures 9 ranges from 100 to 3000 cps at 25° C.The resin transmits more than 75% of the light incident on it.Preferably, the viscosity of the ultra-violet resin lies within therange 500 to 1500 cps at 25° C., and the transmissivity of the resin ismore than 85%. Although the rein could be sufficiently spread on thesurface of a shaping roller 12, when the viscosity is less than 100 cps,process control would not be easy and a significant amount oflow-boiling point material would be lost. If the resin's viscosity weremore than 3000 cps, spray coating process would be difficult and airbubbles could well be formed because the shaping roller 12 would not besufficiently wet by the resin.

[0025] Materials which may be used for the ultra-violet resin of thegrating 7 and the lenticular structures 9 include: urethane acrylateresin, epoxy acrylate resin, ester acrylate resin, ether acrylate resin,and mixtures thereof.

[0026] The transparent substrate 8 of the Fresnel lens 4, thetransparent substrate 10 of the objective lens 5, and the protectivesheet 6 preferably have thickness of 10-250 μm, light transmissivity of75% or more and a tensile strength of at least 600 kg/cm², and morepreferably thickness of 50-150 μm, light transmissivity of 85% or moreand a tensile strength of at least 1000 kg/cm². If the thickness wereless than 10 μm or the tensile strength less than 600 kg/cm², the screen1 could be easily damaged and the film tom during the preparation of thescreen. If the thickness were more than 250 μm, the total thickness andweight of the screen 1 would be too great and the advantages ofemploying a film in the present invention would be lost. If thetransmissivity were less than 75%, the transmissivity the screen 1 wouldbe too low.

[0027] Materials which may be used for the transparent film of thesubstrate 8 of the Fresnel lens, the substrate 10 of the: objectivelens, and the protective sheet 6 include: polyester, polyestersulfon,polyamide 6, polyamide 66, polycarbonate, polyestersulfon, polyesterketone, polyesterimide, polyacrylate, and mixtures thereof.

[0028]FIG. 4 illustrates an apparatus for making shapes on one surfaceor both surfaces of the substrate of the Fresnel lens 4 and theobjective lens 5 according to the present invention, the apparatuscomprising a shaping roller 12; a device 13 for applying liquid resin tothe substrate; an ultra-violet irradiating device 14; and a roller 15for supplying the substrate film. The shaping roller 12 is easilyreplaceable in order to impress one surface or both surfaces of thesubstrate with various shapes.

[0029]FIG. 5 illustrates a conventional apparatus used for manufacturingan objective lens. In FIG. 5, a film extruded by an extruder 17 isshaped by a shaping roller 12 and thereafter cooled by a cooling roller18 and drawn by a drawing roller 19. Such an apparatus cannot be usedfor manufacturing a thin-film objective lens.

[0030]FIG. 6 illustrates a conventional process of manufacturing aFresnel lens. In the process shown in FIG. 6, a liquid ultraviolet resin21 is poured into a flat mold 20 to shape a Fresnel lens. The flat mold20 is then covered with a panel 22 which forms the substrate of theFresnel lens The resin 21 is passed through a roller 23 and is exposedto an ultra-violet irradiating device 14. The conventional method ofFIG. 6 is not applicable to mass production and the process can beoperated only in a batch mode. A thin-film type substrate could noteasily be used in the method illustrated by FIG. 6.

[0031]FIG. 7 illustrates a conventional process of manufacturing aFresnel lens using a press. In the process shown in FIG. 7, a Fresnelsubstrate 25 is inserted between the flat mold 20 and a planar upper die24. The Fresnel substrate 25 is then heated, pressed, rolled andreleased. However, this press process has the disadvantages of longmanufacturing time, and short duration of the die, and consequent lowproductivity.

[0032]FIG. 8 illustrates a process of manufacturing a shaping roller forforming a Fresnel lens and an objective lens according to an embodimentof the present invention. According to the present invention, theFresnel lens 4 and the objective lens 5 can be manufactured incontinuous mode due to the use of a roll shaped die rather than theplanar die of the prior art.

[0033] The electroforming method illustrated in FIG. 8 may be used, formanufacturing a shaping roller. In FIG. 8, a silicone rubber die mold 26is patterned using a planar die 20. The patterned silicone rubber diemold 26 is made into a tube-type die by a reinforcing steel tube 27.After a metal electroforming die 28, made, for example, of nickelchromium has been fabricated at the inner side of the tube-type siliconerubber die mold 26 by means of an electroforming method, the reinforcingsteel tube 27 is removed, which leaves only the electroformed metal die28. Finally the shaping roller is completed by inserting and fixing acylindrical steel tube roller with shaft into the electroformed metaldie 28.

[0034] The invention described above will be more fully understood withreference to the following Example and Comparative Example.

EXAMPLE

[0035] Urethane acrylate resin is used as the ultra-violet resin of thegrating 7 and the lenticular structures 9. Polyester film is used forthe substrate 8 of the Fresnel lens, the substrate 10 of the objectivelens, and the protective sheet 6. The properties of urethane acrylateresin and polyester film used in the present example are summarized intables 1 and 2, respectively.

[0036] The process conditions are as follows:

[0037] surface temperature: 35±5° C.; and

[0038] manufacturing speed: 4 to 7 n/min.

[0039] Comparative Example

[0040] A comparative product is manufactured as a prior art product.Polymethylmetacrylate is used for the substrate 8 of the Fresnel lensand the substrate 10 of the objective lens. Urethane acrylate is usedfor the grating 7. TABLE 1 Properties of Urethane Acrylate Resin used inFresnel lens and lenticular lens Item Properties Remarks CompositionUrethaneacrylate Sunkyung-UCB Co., Ltd. Viscosity (cps) 950 ± 50 25° C.Transmission rate of 91 ± 1 total amount of light (%) Index ofReflection 1.52 ± 0.02 Specific Gravity 1.1

[0041] TABLE 2 Properties of Polyester Film used in Protective SheetItem Properties Remarks Composition Polyester SKC Co., Ltd. Thickness(μm) 200 protective sheet 100 Fresnel lens 50 lenticular lens Index ofReflection 1.64 ± 0.01 Transmission rate of 91 total amount of light (%)Specific Gravity 1.4 Tensile Strength 2,500 ± 50   (Kg/cm²)

[0042] TABLE 3 Properties of the Screens Example Comparative Item 1Example 1 Weight protective sheet (6) 160 1260 (gr) Fresnel lens (4) 140504 objective lens (5) 191 1250 total 491 3014 Thickness of Screen (mm)0.85 5.00 Tensile protective sheet (6) 2500/2500 550/550 *PolyesterStrength Fresnel lens (4) 2200/2200 480/480 film (Kg/cm²) objective lens(5) 2100/2050 500/120 0° direction (90° direction) Transmission rate oftotal 89 85 amount of light (%) Particulars Screen (1) diagonal length:43 inch Aspect ratio = 4:3

[0043] As can be seen from Table 3, the projection tv screen 1 accordingto an embodiment of the present invention weights of 84% less and hastensile strength 4.5 times greater than conventional television screen.

What is claimed is:
 1. Projection television screen comprises: a) a Fresnel lens comprising a first transparent substrate comprising a transparent synthetic resin film, and a phase grating; b) an objective lens, adjacent to and optically aligned with the Fresnel lens, comprising a second transparent substrate and a plurality of lenticular structures mounted on both surfaces of the second substrate comprising a transparent synthetic resin film; and c) a transparent protective sheet, adjacent to the surface of the objective lens furthest from the Fresnel lens, comprising a transparent synthetic resin film, and absorbing stray ambient light and thus brightening the images on the screen, wherein the phase grating, mounted on the surface of the first substrate nearest the objective lens, comprises a resin that is cured by exposure to ultra-violet light after the shape of the grating has been impressed upon the resin, and wherein the Fresnel lens collimates light from an image protector and uniformly projects the collimated light onto the surface of the objective lens nearest the Fresnel lens, and the objective lens collects parallel red, green, and blue image beam from the Fresnel lens at a predetermined position of each of color cell.
 2. The projection television screen as recited in claim 1, wherein said synthetic resin film has a range of thickness from 10 to 250 μm, a transmission rate of the total amount of light 75% or more, and a tensile strength of 600 Kg/cm² or more.
 3. The projection television screen as recited in claim 2, wherein said synthetic resin film has a range of thickness from 50 to 150 μm, a transmission rate of the total amount of light 85% or more, and a tensile strength of 1000 Kg/cm² or more.
 4. The projection television screen as recited in claim 2 or claim 3, wherein said synthetic resin film is made of one or more resin selected from the group consisting of polyester, polyvinylchloride, polyamide 6, polyamide 66, polycarbonate, polyestersulfon, polyester ketone, polyesterimide, and polyacrylate.
 5. The projection television screen as recited in claim 1, wherein said resin that is cured by exposure to ultra-violet light is a liquid resin having a viscosity ranging from 100 to 3000 cps at 25° C. and a transmission rate of the total amount of light 75% or more.
 6. The projection television screen as recited in claim 5, wherein said resin is a liquid resin having a viscosity ranging from 500 to 1500 cps at 25° C. and a transmission rate of the total amount of light 85% or more.
 7. The projection television screen as recited in claim 5 or claim 6, wherein said resin is selected from the group consisting of urethane acrylate, epoxy acrylate, ester acrylate, and ether acrylate resins.
 8. The projection television screen as recited in claim 5, wherein said resin further comprises a diffusing agent.
 9. The projection television screen as recited in claim 1, wherein the objective lens further comprises an anti-reflective layer mounted on the substrate opposite to the Fresnel lens.
 10. The projection television screen as recited in claim 9, wherein said anti-reflective layer comprises a black ink that is cured by exposure to ultra-violet light.
 11. A process for fabricating a shape forming roller for manufacturing a screen for a projection television receiving set comprising the steps of: a) patterning a flat plate die into a silicone rubber mold die; b) making said patterned silicone rubber mold die into a tube-type die by a reinforcing tube; c) fabricating an electroforming die made of metals at the inner side of the tube-type silicone rubber mold die; d) removing the silicone rubber mold die and the reinforcing tube leaving only the electroformed metal die; and e) manufacturing a forming roll by inserting and fixing a cylindrical steel tube roll with shaft into the electroforming metal die.
 12. A manufacturing process for making shapes on one or both surfaces of a substrate of a Fresnel lens and a lenticular lens, using a system comprising a shape forming roller, a device for applying liquid state resin, a ultra-violet ray irradiating device, and a roller for supplying the substrate film, said shape forming roller is fabricated by the steps comprising: a) patterning a flat plate die into a silicone rubber mold die; b) making said patterned silicone rubber mold die into a tube-type die by a reinforcing tube; c) fabricating an electroforming die made of metals at the inner side of the tube-type silicone rubber mold die; d) removing the silicone rubber mold die and the reinforcing tube leaving only the electroformed metal die; and e) manufacturing a forming roll by inserting and fixing a cylindrical steel tube roll with shaft into the electroforming metal die. 